1. Field of the Invention
The present invention relates to a drive device for auxiliary machines provided in an engine for an automobile. More specifically, the present invention relates to an improvement on an auxiliary machine drive device for an engine, on a rear end portion or on a rear end surface of an engine body.
2. Background Art
An engine for an automobile is provided with a variety of auxiliary machines, Patent Literature 1 (Japanese Unexamined Patent Publication No. 2007-046480) discloses the following configuration, as an example of an auxiliary machine drive device for an engine. A first crankshaft sprocket and a second crankshaft sprocket are mounted on a crankshaft on the side opposite to the output side of the camshaft with respect to a transmission (on the front side of an engine body); a first intermediate sprocket and a second intermediate sprocket are coaxially mounted above the crankshaft; a camshaft drive lower chain is wound between a fuel pump driving sprocket disposed laterally of the crankshaft, the first crankshaft sprocket, and the second intermediate sprocket; a camshaft drive upper chain is wound between an intake camshaft drive sprocket, an exhaust camshaft drive sprocket, and the first intermediate sprocket; and a balancer shaft drive chain is wound between a balancer shaft drive chain sprocket disposed laterally of an oil pan, and the second crankshaft sprocket. In other words, the auxiliary machine drive device transmits a rotational driving force of the crankshaft to the fuel pump via the camshaft drive lower chain, and transmits a rotational driving force of the crankshaft to the balancer shaft (balancer device) via the balancer shaft drive chain. Further, the rotational driving force of the crankshaft is transmitted to an intake camshaft and to an exhaust camshaft via the camshaft drive lower chain and the camshaft drive upper chain,
The auxiliary machine drive device disclosed in Patent Literature 1 is disposed on the front side of the engine body. In recent years, there is proposed a configuration, in which the auxiliary machine drive device is disposed on the rear side of an engine body i.e. on the output side of an engine with respect to a transmission. In this case, in view of a positional relationship with the transmission, there is a demand for compacting the auxiliary machine drive layout on a rear end portion or on a rear end surface of the engine body, and for suppressing an increase in the size of the engine, and consequently an increase in the weight of the engine. Particularly, the auxiliary machine drive device disclosed in Patent Literature l is configured to transmit a rotational driving force of the crankshaft to the camshaft, the fuel pump, and the balancer device via the camshaft drive upper chain, the camshaft drive lower chain, and the balancer shaft drive chain. These chains are offset in the axis direction of the camshaft (cylinder array direction). As a result, in the auxiliary machine drive device, the occupation space in the cylinder array direction is likely to increase.